Why do we test for total coliforms and fecal coliforms in water?

To
put it briefly, these organisms are good indicators of the potential contamination
of a water source. Coliform bacteria have been used to evaluate the general
quality of water. Testing for coliform bacteria is faster and cheaper
than testing for specific organisms and pathogens. U.S. Public Health
Service established a standard in 1914. Coliforms include all aerobic
and facultatively anaerobic, gram-negative, non-sporeforming bacilli that,
when incubated at 35 C, can ferment lactose and produce gas (CO2) within
48 hrs. Fecal coliforms are the coliform bacteria that originate specifically
from the intestinal tract of warm-blooded animals (e.g., humans, beavers,
racoons, etc.).

They
are cultured by increasing the incubation temperature to 44.5 C and using
somewhat different growth media. Two other groups of bacteria that are
present in feces are: fecal streptococci and Clostridium. Clostridia spores
can survive a long time during adverse conditions. This genera occurs
naturally in soils and polluted waters; it is not used for monitoring
purposes. Fecal streptococci and enterococci are terms that have been
used interchangeably; however, there are some differences between the
two groups.

Coliform
organisms are used as indicators of water pollution. The coliform organism
is a very common rod-shaped bacterium, not thought of as disease causing
to humans. Because pathogenic bacteria in wastes and polluted waters are
usually much lower in numbers and much harder to isolate and identify
than coliforms, which are usually in high numbers in polluted water, total
coliforms is used as a general indicator of potential contamination with
pathogenic organisms. However, many coliform bacteria live in the soil,
and these organisms may be the source of those that appear in water, especially
surface water. Fecal coliforms, on the other hand, are more specific because
they refer to the coliforms that live in the intestinal track of humans
and many other animals.